Little is known about Martin Erhard: in the 1970s he lived in Peissenberg in the very heart of the Upper Bavarian district of Weilheim-Schongau, where he worked in the local coal mine. He generally preferred the night shifts underground. He had no wife nor children. Those who remember him recall him often wearing rubber boots. All in all, Erhard seemed to be an unremarkable kind of guy. It is said that he liked to draw on the tunnel walls and on the mining carts down in the coal shafts.

What strikes one the most when faced with Martin Erhard's work is the dichotomy between the world portrayed on the surface and the world that dwells down below: there is the cartographical landscape that stretches for over 50 DIN A2 sheets and which covers an area of around 75 square meters - a detailed topological survey along a seamlessly endless train track depicting fields, boundaries, train stations and the occasional shaft to the tunnels below.

And then there is the underground: a series of blueprints for rooms that Erhard devised in what could be conceived for below the ground. These fantastic psycho-architectural drawings show rooms for the "exercise of sexuality of all kinds according to desire and sexual appetite" (Ausübung von Sexualitäten aller Arten nach Wunsch und Trieblust), for "male perverts" and for "sadistic females", or for sports, exercises and art, as well as for the purpose of indulging in sinful pleasures (Haus für Nachholung Sport, Übung und Kunst sowie zum Schauvergnügen mit sündhafter Geniessbarkeit).

Alongside with these works there is selection of self-observation documentation written by the artist - an attempt to make sense of the duality of the discreet, disturbed and private universe of Martin Erhard. Erhard's work is included in the Collection of Arnulf Rainer.